Federal and state regulations often require persons working at elevated heights to utilize fall-arrest equipment. Fall-arrest equipment commonly includes a body harness for attaching to a user and a lanyard for connecting to an anchorage point. Often, the final connection to the anchorage point is made with a hook or a carabiner at the end of the lanyard. Although, regardless of the type of connection, the connector must be manufactured to meet American National Standards Institute (ANSI) and Occupational Safety and Health Administration (OSHA) standards for minimum strength requirements for the hook body, gate/latch and locking mechanism. Additionally, other standards may also apply, for example, depending on the connectors intended use.
Safety hooks typically include a hook body, release lever (also known as a lock lever) and a gate. Additionally, safety hooks typically include springs and fasteners that hold the body, gate and release lever together and in a locked position. The release lever or lock lever of a hook is arranged to shift the locking mechanism away from the gate to allow the gate to open. The gate of a hook is arranged to prevent the hook from disengaging from an anchorage point, while the locking mechanism prevents the gate from opening unintentionally.
Under ideal circumstances, when a person falls, the connector, e.g., the hook, hangs vertically and the force of the fall is absorbed along the principal axis of the hook body. However, anchorage points vary greatly from specifically engineered hardware, to structural elements in buildings and fabrications, to even tree limbs. Because of the wide range of anchorage situations, and the variety of positions a person may be in when they fall relative to the anchorage point, the hook may be prevented from moving to its ideal vertical hanging position. In such situations, forces from the fall may act against the gate/latch and/or locking mechanism, which in the majority of hooks are not as strong as the hook body. Component failure and personal injury are often results of such falls, thus the need for latching mechanisms that can withstand greater forces.
Current ANSI and OSHA standards require hooks and carabiners to be self-closing, self-locking and capable of being opened only by at least two consecutive deliberate actions. Proposed new ANSI standards, e.g., Z 359.1-07ED, significantly change specifications for fall-arrest hardware. The following table summarizes recent proposed changes to the aforementioned standard:
TABLE 1HardwareExistingProposedFeatureTest descriptionstandardStandardGate faceLoad test for strength of gate250 lbs3,600 lbsand locking mechanismGate sideLoad test for strength of gate in350 lbs3,600 lbsresisting side loads
Hook bodies are most commonly constructed of heat treated carbon steel, forged or stamped, while the gate and lock lever are often constructed of stamped mild steel. However, one of ordinary skill in the art will recognize that other materials may also be used depending upon the desired strength of the assembled hook. For example, safety hooks that do not need to meet the described ANSI test standards may have molded plastic bodies, gates or release levers. Most prior art hooks act on the principal that force applied to the gate and lock, i.e., gate face load, is resisted by the strength of the gate and lock lever material and the rivets or fasteners they pivot on. Depending on the configuration of the mechanism, the force applied against the gate face, and transferred to the lock, can be multiplied by the ‘lever nature’ of both the gate and the lock lever, so that 3,600 lbs can become 5,000+ lbs. Due to the configuration of these mechanisms, much of this load is applied against the rivets or fasteners of the gate and lock lever.
Some gates of prior art hooks can withstand 3,600 lb gate side loads, while others can be easily modified to withstand these loads, by constructing existing gates out of thicker heat treated materials, however such modifications increase cost, size and/or weight of a hook. Contrarily, gates are not so easily modified to withstand face loads, i.e., loads applied to the face of the gate which transmit from the gate to the locking mechanism and lock lever and subsequently to the rivets or fasteners on which they pivot and are mounted to the body with. It is impractical or simply impossible to make all elements, of existing hook designs, bigger, thicker or of stronger materials to withstand such loads.
The gates of most carabiners are considerably stronger than the gates of most hooks. The locking mechanism of a carabiner is located in the barrel of the gate, and requires a sliding and/or twisting motion to release the lock and open the gate. This mechanism is relatively expensive to produce and can be difficult to unlock with cold hands or with gloves on and often requires two hands to operate. Contrarily, hooks have relatively simple mechanisms consisting of a gate and a ‘lock-lever’ and can be operated with one hand. Hooks are far more popular because they are easier to use and much cheaper to manufacture.
Thus, there is a long-felt need for a safety hook capable of withstanding elevated, gate face and side loads. There is a further long-felt need for a safety hook having the foregoing characteristics which functions easily and is economical and simple to manufacture.